_isnan

Checks given double-precision floating-point value for not a number (NaN).

int_isnan(doublex);

Routine

Required Header

Compatibility

_isnan

<float.h>

Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.

Libraries

LIBC.LIB

Single thread static library, retail version

LIBCMT.LIB

Multithread static library, retail version

MSVCRT.LIB

Import library for MSVCRT.DLL, retail version

Return Value

_isnan returns a nonzero value (TRUE) if the argument x is a NaN; otherwise it returns 0 (FALSE).

Parameter

x

Double-precision floating-point value

Remarks

The _isnan function tests a given double-precision floating-point value x, returning a nonzero value if x is a NaN. A NaN is generated when the result of a floating-point operation cannot be represented in Institute of Electrical and Electronics Engineers (IEEE) format. For information about how a NaN is represented for output, see printf.